高温高压含CO2气藏偏差因子预测新模型

A new model for predicting the Z-factor of high-temperature and high-pressure CO2-bearing gas reservoir

南海西部莺-琼盆地相继发现了大量(超)高温高压含CO2气藏,亟需开展(超)高温高压条件下CO2对关键流体参数偏差因子的影响研究。对已有8种偏差因子计算模型在研究区的应用效果进行了评价,认为已有模型不适用于莺-琼盆地储层温压条件或仅适用于低CO2含量气藏,而对于高温高压且CO2含量较高的气藏,目前常用方法的计算结果误差均较大。以莺-琼盆地实际高温高压流体偏差因子实验结果为基础,以温度、压力、天然气组分、CO2含量作为输入变量,采用数值非线性最小二乘法建立了一种适用于高温高压含CO2气藏的临界参数校正新模型,并与常规模型进行了对比,结果表明本文新模型对低、中、高含量CO2气藏均具有较高的预测精度,实际预测误差<1.2%。本文研究成果可为类似气藏偏差因子计算提供借鉴。

A large number of high-temperature and high-pressure CO2-bearing gas reservoirs have been successively found in the Ying-Qiong basin of the western South China Sea.Therefore,the study on the impact of CO2 on the Z-factor of key fluids under(super)high-temperature and high-pressure conditions is urgently needed.The existing 8 calculation models of the Z-factor were evaluated and those models were not considered to be suitable for the temperature and pressure conditions of the reservoirs in the Ying-Qiong basin or only suitable for gas reservoirs with low CO2 content.For gas reservoirs with high CO2 content,the calculation results of the commonly used methods all show large errors.On the basis of the actual Z-factor experimental results of the high-temperature and high-pressure fluids in the Ying-Qiong basin of western South China Sea,by taking temperature,pressure,natural gas components and CO2 content as input variables,a new critical parameter correction model suitable for high-temperature and high-pressure CO2-bearing gas reservoirs was established using the numerical Levenberg-Marquardt method,and was compared with those conventional models.The results show that the new model has higher prediction accuracy for low,medium and high CO2 content gas reservoirs,and the actual prediction error is<1.2%.The study results in this paper can provide reference for the calculation of the Z-factor for similar gas reservoirs.